Modules and Visibility

Module Path

Calling a Public Function

A module groups related items. pub makes a function callable from outside the module, and module::item names the path.

Program

Play the program to choose a multiplication factor and call a public function through its module path.

factor
module_path.rs
Replay: real traced execution (multi-file project)
mod math {
    pub fn scale(value: i32, factor: i32) -> i32 {
        value * factor
    }
}

fn main() {
    let factor = 3;
    let result = math::scale(5, factor);
    println!("{result}");
}

mod math {
    pub fn scale(value: i32, factor: i32) -> i32 {
        value * factor
    }
}

fn main() {
    let factor = 2;
    let result = math::scale(5, factor);
    println!("{result}");
}

mod math {
    pub fn scale(value: i32, factor: i32) -> i32 {
        value * factor
    }
}

fn main() {
    let factor = 4;
    let result = math::scale(5, factor);
    println!("{result}");
}

  1. factor ← 3

    7fn main() {8    let facto→ 3r = 3; //@factor=3, 2, 49    let result = math::scale(5, facto3r);10    println!("{result}");

  2. fn scale(value: i32, factor: i32) -> i32

    1mod math {2    pub fn scale(value: i32, factor: i32) -> i32 {3        valu5e * facto3r4    }5}

  3. result ← 15

    8    let factor = 3; //@factor=3, 2, 49    let resul→ 15t = math::scale(5, facto3r);10    println!("{result}");11}
    output15

  1. factor ← 2

    7fn main() {8    let facto→ 2r = 2;9    let result = math::scale(5, facto2r);10    println!("{result}");

  2. fn scale(value: i32, factor: i32) -> i32

    1mod math {2    pub fn scale(value: i32, factor: i32) -> i32 {3        valu5e * facto2r4    }5}

  3. result ← 10

    8    let factor = 2;9    let resul→ 10t = math::scale(5, facto2r);10    println!("{result}");11}
    output10

  1. factor ← 4

    7fn main() {8    let facto→ 4r = 4;9    let result = math::scale(5, facto4r);10    println!("{result}");

  2. fn scale(value: i32, factor: i32) -> i32

    1mod math {2    pub fn scale(value: i32, factor: i32) -> i32 {3        valu5e * facto4r4    }5}

  3. result ← 20

    8    let factor = 4;9    let resul→ 20t = math::scale(5, facto4r);10    println!("{result}");11}
    output20
mod `mod math` defines a nested module.
pub fn `pub fn scale` can be called from outside `math`.
path `math::scale` names the function through the module path.